What is motor neurone disease (MND)?

• A. A reversible condition of the spinal cord.
• B. A progressive degeneration of upper and lower motor neurons causing weakness, atrophy, spasticity, and respiratory failure.
• C. A peripheral nerve demyelinating disease.
• D. A muscular dystrophy of childhood.

Answer: (B)

Motor neurone disease is a progressive neurodegenerative condition in which the motor neurons that control voluntary muscles deteriorate. Because it affects both the upper motor neurons (in the brain) and the lower motor neurons (in the brainstem and spinal cord), people develop a mix of signs: weakness and muscle wasting from lower motor neuron loss, and stiffness or spasticity from upper motor neuron loss. Over time, these effects spread to breathing muscles, leading to respiratory failure. It is not reversible and does not stem from a primary muscle disease or from peripheral nerve demyelination. That's why descriptions that emphasize only spinal cord reversibility, peripheral nerve demyelination, or a primary muscular dystrophy do not fit MND. The best description is a progressive degeneration of both upper and lower motor neurons causing weakness, atrophy, spasticity, and respiratory failure.